Cross flow heat exchanger

ABSTRACT

A cross flow heat exchanger comprising an outer structural frame, a multiplicity of channels longitudinally aligned in parallel spaced relation to form first fluid passageways within the channels, and a multiplicity of wall projection portions formed from the channel side walls and extending outwardly with load-bearing end segments of adjacent side walls abutting and transferring the channel load to the outer structural frame, the channels and wall projection portions arranged for flowing a second fluid normal to and in the space between adjacent channels, and fins extending from the channel edge walls having surface distortions.

[111 3,810,509 [45] May 14,1974

United States Patent 11 1 Kun 3,397,742 8/1968 Jenssen et 165/167 3,590,917 7/1971 CROSS FLOW HEAT EXCHANGER inventor: Leslie C. Kun, Williamsville, NY.

Primary Examiner-Charles .1 Myhre Assignee:

Union Carbide Corporation, New York, N.Y.

Assistant ExaminerTheophil W. Streule, r. Attorney, Agent or Firm.lohn C. LeFever [22] Filed: Mar. 23, 1973 Appl. No.: 344,429

Related U.S. Application Data [63] Continuation-impart of Ser. No. 189,659,0ct. 15, 1971 Pat. No. 3,757,856, and a continuation-in-part of Ser. No. 270,259, July 10. 1972.

fluid passageways within the channels, and a multiplicity of wall projection portions formed from the channel side walls and extending outwardly with loadbearing end segments of adjacent side walls abutting and transferring the channel load to the outer strucd 58 Wm 2 8 m l. 5 6" O SL Um P n 55 [58] Field of Search......................,..... 165/151-l53,

tural frame, the channels and wall projectionportions [56] References Cited arranged for flowing a second fluid normal to and in UNIT-ED STATES PATENTS the space between adjacent channels, and fins extending from the channel edge walls having surface distortions.

165/167 165/167 23 Claims, 51 Drawing Figures 785,580 3/1905 Shiels et 2 281 754 5/1942 Da1zell......... 2,596,008 5/1952 PATENTEDm 14 1914 saw 02 or 22 PATENTEDMAY m 1924 3,810,509

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PATENIEDIAYMIHM 3810.509

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PATENTED m 14 m4 sum 15 or 22 Channels/ft I50 I20 I00 80 6O 40 A Iv-Puxz 2\DPm q EE E E5 5a 2 1 3 E I Projection Height H,inches Heat Transfer Rate per Unit Frontal Area BTU/MIN -FT (Hc1) PAIENTEnm 14 m4 3810.509

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?ATENTED m 14 1914 7 sum 17 0F 22 Channels/ft.

Projection Height H, inches FIG.

PATENTEB m \4 m4 sum 13 0f 22 PATENTEDIAY 14 um CAPACITY, BTU/MlN/FT FRONTAL AREA sum 19 0f 22 80% Sreom ('5 7 (V582 83 Steam in Condensate AIR VOLUME FLOW RATE /FT2 FRONTAL AREA FT3/MIN/ FT 

1. A cross flow heat exchanger comprising: a. an outer structural frame; b. a multiplicity of channels formed of aluminum each having an elongated cross section bound by side walls and edge walls each of between 0.003 and 0.015 inch thickness and an aspect ratio of length to width of an equivalent rectangle equal to at least 4, being longitudinally aligned in parallel spaced relation each with a first fluid entrance opening at one end and a first fluid exit opening at the opposite end, and common inlet manifold means and common exit manifold means respectively for said first fluid entrance openings and said first fluid exit openings, and a multiplicity of wall projection portions formed from each side wall being distributed across the side wall surface and extending outwardly therefrom with load-bearing end segments shaped for mating with and abutting against loadbearing end segments of said projection portions of an adjacent channel side wall thereby spacing adjacent channels with the outermost end segments bearing against and transferring the channel load to said outer structural frame, said wall projection portions having a dimensional size and a dimensional relationship therebetween defined by a D dimension of between about 0.2 and 1 inch, an H dimension of between about 0.02 and 0.14 inch, and a D/d ratio of between about 3 and 18 wherein H equals the maximum height measured perpendicularly from a plane containing the extremity of the projection end segment to a plane containing the most distant point of said side wall surface, D equals the effective spacing between the centers of adjacent wall projection portions of a side wall as determined by the formula: D 3 square root D13 + D23/2 wherein D1 shortest distance between two adjacent wall projection portions in any triangular unit of the projection pattern on tHe side wall, D2 perpendicular distance from a straight line extending through said two adjacent wall projection centers to the center of the third wall projection of the same triangular unit, triangular unit a triangle having a wall projection center only at each of its apexes with each side of the triangle extending between wall projection centers without transversing a shorter line segment interconnecting other projection centers, and d equals the dimension of the ratio 4a/p wherein a equals the area of the load-bearing end segment of the wall-supporting projection and p equals the perimeter of said load-bearing end segment and said wall projection portions also having an elevational contour such that the ratio theta /R is between about 4* and 2,500* per inch wherein theta is the maximum angle of metal in the projection portion with respect to the base plane of said side wall and measured in a cross section passing through the projection portion center perpendicular to the base plane, and R is the minimum radius of curvative of said metal measured outside the projection portion; c. said channels and wall projection portions thereby, and outer structural frame being arranged and constructed for flowing a second fluid through said outer structural frame normal to and in the space between said channels in heat exchange with said first fluid; and d. at least one thin aluminum fin of between 0.003 and 0.015 inch thickness extending at least outwardly from an edge wall of each channel along the entire length thereof, said fins being provided in number and surface area relative to the channel surface area such that the ratio (0C + 0F)/IT of channel outer surface area (0C) plus fin surface area outside said channels (0F) to total surface area inside said channels (IT) is between 1.2 and 4.0, and with each fin having a multiplicity of surface distortions from the fin plane into the gap between adjacent fins of adjacent channels being closely spaced at intervals (S) between 0.01 and 0.2 inch measured to the channel longitudinal axis, so as to comprise a total distortion area which is at least 40 percent of said fin surface area thereby disrupting the second fluid film across the fin width.
 2. A cross flow heat exchanger according to claim 1 wherein the fin surface distortions comprise parallel slats and slotted apertures arranged in a louvered configuration across the fin width.
 3. A cross flow heat exchanger according to claim 1 wherein the fin surface distortions comprise a multiplicity of pleated strips across the fin width and separated by parallel slits, each pleated strip having crests and valleys with apertures formed by the strip edges between said crests and valleys, and with crests, and valleys of adjacent pleated strips being nonaligned in the direction normal to said slits.
 4. A cross flow heat exchanger according to claim 1 wherein the fin surface distortions comprise a series of corrugations having crests and valleys aligned parallel to the channel longitudinal axis and laterally spaced from each other.
 5. A cross flow heat exchanger according to claim 1 wherein the fin surface distortions comprise dimples distributed over the fin surface and separated by undistorted metal, said dimples being aligned in longitudinal rows parallel to the channel longitudinal axis.
 6. A cross flow heat exchanger according to claim 1 wherein at least one fin extends outwardly from each edge wall of each channel.
 7. A cross flow heat exchanger according to claim 1 wherein two fins extend outwardly from each edge wall of each channel.
 8. A cross flow heat exchanger according to claim 1 wherein the ratio (0C + 0F)/IT is between 1.3 and 3.0.
 9. A cross flow heat exchanger according to claim 1 wherein the fin surface distortions are spaced at intervals (S) between 0.02 and 0.10 inch.
 10. A cross flow heat exchanger according to claim 2 wherein the channels are between 0.75 and 2.0 inch wide and the fins are between 0.2 and 0.5 inch wide.
 11. A cross flow heat exchanger according to claim 1 wherein the aspect ratio of said channels is at least
 8. 12. A cross flow heat exchanger according to claim 1 wherein the wall projection portions have an isostress elevational contour.
 13. A cross flow heat exchanger according to claim 1 wherein the wall projection portions have a truncated cone elevational contour.
 14. A cross flow heat exchanger according to claim 1 wherein the wall projection portions have an isostress contour and the fin surface distortions comprise parallel slats and slotted apertures arranged in a louvered configuration across the fin width.
 15. A cross flow heat exchanger according to claim 1 wherein the wall projection portions have a D dimension of between about 0.3 and 0.85 inch, an H dimension of between about 0.025 and 0.1 inch, and a D/d ratio of between about 6 and
 14. 16. A cross flow heat exchanger according to claim 1 wherein the wall projection portions have an isostress elevational contour such that the ratio theta /R is between about 4* and 100* per inch.
 17. A cross flow heat exchanger according to claim 15 wherein the wall projection portions have an isostress elevational contour such that the ratio theta /R is between about 4* and 100* per inch.
 18. A cross flow heat exchanger according to claim 2 wherein the slotted fins are fabricated with an angle of approach theta '' of between 0* and 70*, said angle of approach theta '' being defined as the angle between a first line which is parallel to a plane containing the maximum dimensional width line and the longitudinal dimensional width line and the longitudinal dimensional length line of the channels and perpendicular to the channels'' longitudinal length line, and a second line formed by the intersection of a plane onto the surface of a slat on the slotted fin, said plane being normal to the surface of the slat and containing the first line as defined above.
 19. A cross flow heat exchanger according to claim 18 wherein said angle of approach theta '' is defined as the following: sin theta '' (cos Beta sin gamma -cos gamma sin Beta cos Alpha ) wherein Beta is the angle formed between the plane of the fin and the plane of the slat member between adjacent slotted apertures; gamma is the angle formed between the plane of the fin and a plane containing the maximum width line and longitudinal length line of said channels; and Alpha is the angle formed between the longitudinal length line of the channels and the longitudinal length line of the slot formed between adjacent slats.
 20. A cross flow heat exchanger according to claim 19 wherein said angle of approach theta '' is between 0* and 45*.
 21. A cross flow heat exchanger according to claim 19, wherein said angle of approach theta '' is between 0* and 45*, the maximum dimensional width line of said channels is between 0.75 inch and 2.0 inches, and the fin width is less than 0.6 inch.
 22. A cross flow heat exchanger according to claim 21 wherein the width of the slats of the louvered configuration are at least 0.02 inch.
 23. A cross flow heat exchanger according to claim 21 wherein angle Beta is between 30* and 60*, angle is between 45* and 135*, and angle Alpha is between 0* and 60* . 